None of these ranks bring any new permissions and only the last new rank is bound to a special privilege, so they're purely cosmetical.
Why do we need them?
It's simple: I want to give the high staff members a chance to keep working their way up.
These 4 new ranks are not something that every player is supposed to get sooner or later, these ranks can be compared to level 100 in any generic online MMORPG, where you have to spend multiple years farming XP and loot to get there.
(Except it isn't multiple years on the server.)
I may or may not have a "secret" permission node for the 4th level ranks, but i'll think about that later when someone actually gets one of these.
(Greek Titan of divine law and order.)
(Greek Titan carrying the sky upon his shoulders.)
(Also a greek titan and personification of the earth.)
To avoid further discussions about this:
Yes, the three new 4th level ranks are considered "higher" than agent because they are harder to obtain, even though agents still have more permissions. Agent+ and the new secret rank however are still the 2 highest obtainable ranks and it will always stay that way.